Two matters must be clarified by a rabbinic court before it can accept a convert: 1) Does the convert earnestly intend to join the Jewish people, or does he harbor ulterior motives? 2) Is the convert indeed ready to accept upon himself the yoke of the Torah and its commandments?
When it is clear to a rabbinic court that the answer to these two questions is affirmative, the main part of the conversion process is complete, and the court proceeds to carry out the practical aspects of the conversion. Just as the Jewish people entered a covenant with the Almighty via three acts – circumcision, ritual immersion, and sacrifice – so must the non-Jew who seeks to join us enter the covenant of the Jewish people via circumcision, ritual immersion, and sacrifice.
Because today the Holy Temple does not exist, and it is therefore impossible to offer sacrifices, Jewish law rules that it is possible to convert without offering a sacrifice. Regarding circumcision and ritual immersion, though, there is no change, and one who has not carried out these two acts is not a convert.
The foremost condition of conversion is that the convert accept upon himself the Torah. It is unthinkable that a person convert without embracing the Torah. Just as the Jewish people became a nation by accepting the Torah at Mount Sinai, so must one who wishes to join the Jewish people accept upon himself the Torah as an individual before a rabbinic court.
Therefore, from a legal point of view, the rabbinic court’s main consideration is whether or not the prospective convert is indeed ready to accept the Torah and its commandments. And so long as the rabbinic court is uncertain about the veracity of the convert’s intentions, it is unable to convert him. If, however, the rabbinic court is convinced the convert’s intentions are pure and goes ahead and converts him and the convert subsequently begins to neglect the Torah, he nonetheless continues to be considered Jewish.
Just as a Jew who does not yet observe all of the commandments of the Torah is nonetheless considered Jewish, so a convert who subsequently neglects the Torah remains Jewish.
What if the convert is prepared in principle to accept upon himself the yoke of the Torah and its commandments but believes that from time to time he will have to transgress some of the commandments?
Strictly speaking, it is clear that there is no dispensation for desecrating the Sabbath, even occasionally; neither is it permissible even in difficult conditions to eat forbidden foods. Nonetheless, the eminent R’ Chaim Ozer Grodinski holds that it is possible to convert such a person. This is because we relate to the acceptance of commandments in principle. In principle, the convert has agreed to take upon himself observance of the commandments, and it is only on occasion that he believes he will transgress.
Although there are important authorities who disagree with this opinion, in practice many follow the ruling of Rabbi Grodinski, and if it is clear to the court that the convert accepts the commandments in principle, it is possible to convert him.
Conversion under Reform or Conservative auspices, however, is no conversion at all because the convert does not accept all of the commandments in principle.